One-step thermal polymerization of styrene is known using a disulfide modifier in the presence of azobisisobutyronitrile initiator (Pierson et al, 17 J. Polymer Science 221-246, 1955). U.S. Pat. No. 3,470,146 discloses improved polystyrene beads produced by one-step thermal polymerization of styrene in the presence of a finely divided phosphate suspending agent, a water soluble sulfide or precursor, and certain water soluble organic sulfides. Neither of the above references discloses liquid polymers. Existing processes for production of hydroxyl-terminated liquid polymers are typically two-stage processes, e.g., the processes of U.S. Pat. Nos. 3,712,916 and 3,699,153. An improved one-step process is desired for production of hydroxyl-terminated liquid polymers using a hydroxyl-containing disulfide. Such an improved one-step process is desired in order to reduce expense of viscosity control during polymerization, and to reduce discoloration and odor upon heating of the resulting polymers.